1. Field of the Invention
The present invention relates to a printing apparatus and printing method in which an image can be printed on a relatively rigid printing medium such as cardboard.
2. Description of the Related Art
Heretofore, there have been printing apparatuses including a path for conveying relatively thick paper (cardboard) through a printing position, in addition to a path for conveying relatively thin ordinary paper through the printing position. The path for conveying cardboard is, for example, configured to convey cardboard inserted from the back side of the printing apparatus to the printing position and to eject the cardboard having an image printed thereon at the printing position from the front side of the printing apparatus. However, it is very difficult to insert the cardboard from the back side of the printing apparatus.
In Japanese Patent Application Laid-open No. 2002-348019, a printing apparatus is described which includes a switchback path for conveying cardboard while curving it as little as possible. The printing apparatus has a constitution in which the switchback path is provided at an intermediate point along a path for feeding paper from automatic paper feed means. When ordinary paper is used, the paper is turned over to be conveyed to a printing position. When cardboard is used, the cardboard is conveyed to the printing position through the switchback path while being curved as little as possible.
However, in such a printing apparatus, though cardboard as a printing medium of a certain thickness can be conveyed, it is inevitable that the cardboard will be curved. Accordingly, very thick board paper or the like cannot be conveyed. Moreover, even in the case of cardboard capable of being conveyed, since the cardboard is curved with a certain curvature during the conveyance, there are cases where back tension occurs due to the strong rigidity of the cardboard. In such a case, there is a possibility that the conveyance distance of the cardboard may partially changes to cause image deterioration.
An object of the present invention is to provide a printing apparatus and method, in which a very thick and rigid printing medium such as board paper can be conveyed with stable conveyance accuracy, and in which a high-quality image can be printed thereon.